1. Field of the Invention
This invention relates to a thermal control system capable of rejecting large amounts of heat and maintaining heat generating devices at a substantially constant and uniform temperature without the use of a closed-loop environmental control system (ECS) wherein the use of an expendable fluid to provide the refrigeration effect results in a heat rejection capacity very much in excess of any form of active environmental control unit (ECU) that could be packaged within the constraints of size and available prime power.
2. Brief Description of the Prior Art
Airborne electronic systems normally have thermal control systems which are supplied with a gaseous or liquid coolant from an airborne ECS which is basically a refrigeration system. Since small missiles are unable to provide a self-contained closed-cycle ECS, other means of providing thermal control must be employed. Another prior art form of thermal control has been the use of fins exposed within an air stream. In the recent past, the power dissipation requirement levels of the missile-borne electronic systems have been low enough so that the mass of the missile structure has been used to absorb waste heat during the length of the missile flight. This method of thermal control is acceptable as long as the resultant device temperatures are within acceptable limits and as long as temperature gradients from device to device are not a problem.
Missile-based electronic systems currently under development are projected to have 10 to 100 times the waste heat dissipation requirements of existing systems. Because of power, weight and volume restrictions, a small missile cannot employ an ECS large enough to dissipate the magnitudes of power of the next generation of missile-based electronic systems. In addition, as the complexity and performance of electronic assemblies increases, it becomes essential that devices operate at a specified and uniform temperature to ensure calibrated performance. This is particularly true of phased array radars that contain a large number of substantially identical devices in the array that must have substantially identical performance characteristics.
With the foreseeable requirement of airborne electronic systems to reject a very high level of heat relative to present airborne electronic systems at a specified temperature which must be uniform over a large spatial distance without the benefit of ECS, it becomes apparent that conventional thermal control techniques as discussed above will not work adequately and that innovative methods not previously employed must be developed.